I looked up Eisenhaus on the webEisenhaus
they sell Eisenmann exhausts
that caused the misunderstanding
if Shahab says they're fake it miht mean they sell fake Eisenmann exhausts

Eisenmann is a quality German manufacturer of exhaust systems
for Germany, they quote prices between 800 and 1250 Euros for M3 exhaust systems
that's between $1250 and $2000
but of course you better check the US prices, I just posted these for comparison